Abstract

Liquid removal from gas wells is needed as reservoir pressure declines resulting in lower gas flow rates. As liquids accumulate in the wellbore, the hydrostatic pressure due to the liquid column exerts a backpressure on the producing sand face resulting in lower production rates. As additional liquids enter the wellbore, the well will cease to flow. By removing these liquids, gas production is maintained. Since various artificial lift techniques are used to produce these liquids, it is important that the lifting method be compatible with the size of the completions. The purpose of the paper is to discuss which options are available to lift liquids from slim-hole gas wells.

Introduction

The methods presented in this paper for lifting liquids from slim-hole completions deal with casings sizes ranging from 2–3/8 in. to 2–7/8 in.1 These methods for lifting liquids from these gas wells are:

  1. beam pumps,

  2. progressive cavity pumps,

  3. gas lift,

  4. hydraulic jet pumps.1,2,3

Progressive cavity pumps (PCP) may be installed within 4–1/2 in. casing with small pumps. Completion details and sizes of the various pumps and lifting systems downhole are discussed below.

The production rates for beam pumping installations can range from 500 BFPD from 3000 ft to 100 BFPD from 6000 ft well with a 1–1/4 in. pump. In comparison, PCP can deliver 400 BFPD in 5–1/2 in. casing with 3–1/2 in. tubing. This rate would decline 50 BFPD for 2–3/8 in. tubing set to 5000 ft. Gas lift rates vary from 150 to 200 BFPD in 3/4 in. I. D. tubing to 900 BFPD in 1–1/2 in. I. D. tubing. Slim hole hydraulic jet pumping can produce 100 BFPD from 2500 ft with 1 in coiled tubing (CT) employed as the power fluid string, and 1–1/4 in. CT acting as the return string in 2–7/8 in. completion. Additionally, a slim hole jet pump can produce 250 to 300 BFPD with 1–1/4 in. CT inside 2–3/8 in. from 3800 ft. Using a 2–1/16 in. CT for power fluid string inside of 3–1/2 in. tubing production rates as high as 1200 BFPD from 5200 ft can be realized. These summary figures are approximate and need to be evaluated on a well-by-well basis.

Slim Hole Completions with Beam Pump

Beam lift is the most common method of artificial lift with a rotary motor motion converted to reciprocal motion at the surface by the surface unit. The surface unit reciprocates a string of steel sucker rods to actuate a downhole pump. Most beam pump installations use 2–3/8 in. or 2–7/8 in. tubing in 4–1/2 in. to 7 in. casing. There are many instances where it is necessary to install a beam pump into a slim hole completion for lifting fluids from liquid loaded gas wells.

Casing pump & hollow rods completions

For slim hole applications with beam pump, there are two possibilities. One is to simply land the pump with an insert anchore inside small casing (as small as 2–3/8's or 2–7/8's) and produce the fluid through the pump with a casing pump. The other possibility is to use a tubing insert anchore with the rubbers stripped out of the anchor and let gas bypass the pump. In this situation, gas bypasses the pump while fluid is produced from the hollow rods. Hollow rods were more common in the past; however, they are more difficult to obtain at the present time. This arrangement is shown in Fig. 1.

Small tubing inside small casing

Another possibility, which allows gas venting, is to use very small tubing within a 2–7/8 in. completion. A small string of rods is run inside the small tubing.

Casing pump & hollow rods completions

For slim hole applications with beam pump, there are two possibilities. One is to simply land the pump with an insert anchore inside small casing (as small as 2–3/8's or 2–7/8's) and produce the fluid through the pump with a casing pump. The other possibility is to use a tubing insert anchore with the rubbers stripped out of the anchor and let gas bypass the pump. In this situation, gas bypasses the pump while fluid is produced from the hollow rods. Hollow rods were more common in the past; however, they are more difficult to obtain at the present time. This arrangement is shown in Fig. 1.

Small tubing inside small casing

Another possibility, which allows gas venting, is to use very small tubing within a 2–7/8 in. completion. A small string of rods is run inside the small tubing.

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